1. Field of the Invention
The present invention relates to a novel, simple and accurate apparatus for use in a method such as disclosed in my copending application Ser. No. 07/668,237 for studying interaction of a native ligand and its receptor. Such a method uses a fluorescently labeled, indicator ligand and a porous, optically transparent matrix that can be permeated by the fluorescently labeled ligand but is partially or totally impermeable to the labeled ligand when it is bound to the receptor. Fluorescence emitted from within the porous matrix is useful as an indicator of the interaction between the native ligand and the receptor.
2. State of the Art
Interaction of a ligand and a receptor in solution has been assayed or studied in the past by complicated techniques using differently labeled components. One such method is to use a radioactively labeled ligand or receptor. Another method is to utilize a fluorescent dye that is attached to the ligand or receptor. Generally, however, it has been necessary to isolate the reactants or products by complicated procedures. For example, special procedures have been necessary to separate bound from unbound ligands.
In U.S. Pat. No. 4,816,419 a method for fluorescence ligand binding assays is disclosed wherein certain surfactants that form micelles in solution were found to be useful in effecting differential fluorescence between bound and unbound ligands. The micelles sequester bound from unbound labeled ligands. Capture of labeled ligands occurs preferentially for free labeled ligands. When the labeled ligands are bound to a receptor, capture by the micelles is severely inhibited. The fluorescent emission is different when the labeled ligands are captured by the micelles than when the bound labeled ligands are not captured.
The method using the micelles of U.S. Pat. No. 4,816,419 is severely restricted in the breadth of ligands and receptors that can be analyzed or studied. The method employing the micelles is chemical in nature, thereby being restricted to the study of ligands and receptors bound to the ligands that interact in specific ways with the micelles. The ligands must be bound to or combine with the micelles, and the ligands bound to the receptor must not be attracted to or combine with the micelles.
In my copending application Ser. No. 07/668,237, a novel, simple, accurate, fast, economical method is disclosed for studying and assaying the interaction of two molecules, such as a ligand and its receptor, in solution utilizing the measurement of fluorescence within an optically transparent matrix that is differentially permeable to the molecules depending upon the size of the molecules. In the method of my copending application, a fluorescently labeled molecule is used that can permeate a porous, translucent or transparent matrix, with the reaction product of the labeled molecule and the other molecule being partially or totally excluded from the matrix. The matrix can then be viewed, such as through a fluorescence microscope, to determine fluorescence emitted from within the matrix.
3. Objective
The principal objective of the present invention is to provide novel apparatus for use in the method disclosed in my copending application Ser. No. 07/668,237.